"outfront" tonight, national security contributor fran townsend who is on the cia and homeland security external advisory board and noah shachtman. noah, what do we think is going on right now? at what point are they in this process? >> so the assad regime has hundreds of metric tons of the building blocks of sarin. basically two big building blocks. there's isopropanol which is rubbing alcohol and phosphorous compounds. those are kept separately in order to keep things safe. but the assad regime in small, limited quantities appears to have combined those two chemicals to make deadly sarin nerve agent and has loaded them on to aerial bombs. >> if that is true, fran, it's a very provocative thing. is it provocative enough that the u.s. now has to consider action? >> well, you know, the administration has not made it clear. what the president has said is that the use of such weapons would be a red line for the united states and her allies. but it's not clear, short of use, is this preparation, is the mixing of the precursor chemicals enough? as noah can tell you this is a very unstable su